Our invention relates to speed control apparatus for railroad trains. More particularly, the invention pertains to a velocity control arrangement on board a railroad train or locomotive which calculates a maximum allowable speed in accordance with a stopping distance based on the advance traffic condition signal received from the wayside signal system and controls the train speed so as not to exceed this calculated maximum speed.
Speed control systems for railroad trains exist in several forms. However, in the known arrangements, a maximum permitted speed is arbitrarily assigned for each different cab signal aspect or indication received from the wayside signal system. Each such cab signal indication designates a different traffic condition along the track in advance of the moving train or, in effect, each indication designates a point in advance at which the train must be prepared to stop. Since the permitted speed level is preset in accordance with the cab signal aspects, the same level must always be enforced when the corresponding cab signal indication is displayed. This somewhat limits the most effective operation of the train since variations in the track parameters through the advanced stretch, e.g., ascending or descending grade curvature, make stopping distances from the same speed vary. Also, various train parameters have an effect on the stopping distance. If traffic conditions, track characteristics, and individual train parameters can all be incorporated into the maximum speed allowed for each signal indication, a more efficient operation of the train may be achieved. This process requires the continuous calculation of a maximum train speed, from which the train's braking capabilities stop the train within the indicated clear track, and comparing that allowable speed with the existing speed to inhibit an overspeed situation. Such calculations and comparisons require the on-board processing of all existing information, that is, cab signal indication, existing train speed, advance traffic and track conditions, train parameters, etc. However, with the present availability of small size data processors, it is possible to use such devices on board the train or locomotive to accomplish the determination of the maximum speed allowable at each instant in accordance with all the listed factors. Such speed calculations and maintenance of that speed restriction provide a distinct advantage in train operation.
Accordingly, an object of our invention is speed control apparatus for railroad trains which calculates a maximum allowable speed in accordance with the stopping distance indicated by a received cab signal indication with due consideration of known train and track parameters.
Another object of the invention is a data processing arrangement for controlling the speed of a railroad train in accordance with a maximum speed determined from the received wayside signal indication, the advance track and train parameters, and the current or existing train speed.
A still further object of the invention is a processing means for use on a railroad train which calculates a maximum allowed train speed at which the available braking capability will stop the train within the unoccupied distance indicated by the received wayside signal, compares the maximum speed signal thus calculated with the existing train speed signal received from speed sensing means, and provides a permissive operating signal while the existing speed is less than the calculated maximum speed.
Yet another object of the invention is speed control apparatus for a railroad train in which each of a pair of processing devices calculates a maximum speed from which train braking is capable of stopping the train within the clear track distance in advance indicated by the advance traffic condition signal received from the wayside, each processing device further comparing the calculated speed with the current train speed received from sensing elements on board the train and outputting a selected signal into a logic network as the train speed is less than, or equal to, or greater than, the maximum calculated speed, the logic network processing the output signals to hold off the train braking only when the signal received from each processing device indicates that the maximum speed is not exceeded.
Also an object of our invention is speed control apparatus for a railroad train including a pair of processing units, each coupled to receive a signal representing the current train speed, a signal indicating advance traffic conditions, and signals representing specific parameters of the train, and functioning to determine a critical speed from which the train brakes can stop the train within the available clear distance designated by the received advance traffic signal and to compare this critical speed with the current speed to develop an output signal of predetermined characteristics only when the current speed is less than the critical speed; and a logic network for receiving the processing unit output signals and controlling train brakes to stop the train if each output signal does not have the individual predetermined characteristic.
Other objects, features, and advantages of our invention will become apparent from the following specification and appended claims when taken in connection with the accompanying drawing.